Our goal is to understand the underlying mechanisms regulating lineage specification of hematopoietic stem cells (HSC) and vascular angioblast cells from mesoderm during embryogenesis. As an entry point to achieve this we have chosen to study two molecular factors that are expressed during the early stages of blood and vessel development in zebrafish, ETSRP and DUSP5. The main goal of this proposal is to identify the molecular targets of a novel transcription factor expressed in hemangioblasts, ETSRP, by adopting the newly developed Chromatin Immunoprecipitation-Sequencing (ChlP-Seq) approach, whereby the chromatin regions bound by a transcription factor are immunoprecipitated, amplified and quantified by direct sequencing. Chromatin regions with reads above a predetermined threshold are then computationally mapped to their locations in the genome to identify the targets. This approach is applicable to zebrafish as its genome sequence has recently become available through public databases. Zebrafish is also a superb system for such an application because through subsequent bioinformatics, expression, and functional studies, the potential targets can be validated in vivo and placed in the context of developmental genetic networks. As an example of this validation process, we will examine one genetic entity that is genetically downstream of ETSRP and whose expression pattern is blood and vessel specific, Dual Specific Phosphatase, DUSP5, Both loss and gain of function approaches will be used for this purpose, and it's functional relevance will be examined if it is found to be relevant to circulatory development. These projects bear significant relevance to public health because various clinical disorders such as cancer, rhematoid arthritis, and ischemias either rely on circulatory formation or are caused by problems with circulation. Medicinal approaches to alleviate such disorders depend on careful and methodical research, and basic scientific research such as the work proposed here is focused on providing future therapeutic development with valuable information on the biology of circulation